In the prior art, a hybrid encoder is usually used to encode an audio signal in a voice communications system. Specifically, the hybrid encoder usually includes two sub encoders. One sub encoder is suitable to encoding a speech signal, and the other sub encoder is suitable to encoding a non-speech signal. For a received audio signal, each sub encoder of the hybrid encoder encodes the audio signal. The hybrid encoder directly compares quality of encoded audio signals to select an optimum sub encoder. However, such a closed-loop encoding method has high operation complexity.